content: /*
   * Copyright (C) 2007 Esmertec AG.
   * Copyright (C) 2007 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package spam.blocker.util.pdu.pdu;
  
  
  public class Base64 {
      /**
       * Used to get the number of Quadruples.
       */
      static final int FOURBYTE = 4;
  
      /**
       * Byte used to pad output.
       */
      static final byte PAD = (byte) '=';
  
      /**
       * The base length.
       */
      static final int BASELENGTH = 255;
  
      // Create arrays to hold the base64 characters
      private static byte[] base64Alphabet = new byte[BASELENGTH];
  
      // Populating the character arrays
      static {
          for (int i = 0; i < BASELENGTH; i++) {
              base64Alphabet[i] = (byte) -1;
          }
          for (int i = 'Z'; i >= 'A'; i--) {
              base64Alphabet[i] = (byte) (i - 'A');
          }
          for (int i = 'z'; i >= 'a'; i--) {
              base64Alphabet[i] = (byte) (i - 'a' + 26);
          }
          for (int i = '9'; i >= '0'; i--) {
              base64Alphabet[i] = (byte) (i - '0' + 52);
          }
  
          base64Alphabet['+'] = 62;
          base64Alphabet['/'] = 63;
      }
  
      /**
       * Decodes Base64 data into octects
       *
       * @param base64Data Byte array containing Base64 data
       * @return Array containing decoded data.
       */
      public static byte[] decodeBase64(byte[] base64Data) {
          // RFC 2045 requires that we discard ALL non-Base64 characters
          base64Data = discardNonBase64(base64Data);
  
          // handle the edge case, so we don't have to worry about it later
          if (base64Data.length == 0) {
              return new byte[0];
          }
  
          int numberQuadruple = base64Data.length / FOURBYTE;
          byte decodedData[] = null;
          byte b1 = 0, b2 = 0, b3 = 0, b4 = 0, marker0 = 0, marker1 = 0;
  
          // Throw away anything not in base64Data
  
          int encodedIndex = 0;
          int dataIndex = 0;
          {
              // this sizes the output array properly - rlw
              int lastData = base64Data.length;
              // ignore the '=' padding
              while (base64Data[lastData - 1] == PAD) {
                  if (--lastData == 0) {
                      return new byte[0];
                  }
              }
              decodedData = new byte[lastData - numberQuadruple];
          }
  
          for (int i = 0; i < numberQuadruple; i++) {
              dataIndex = i * 4;
              marker0 = base64Data[dataIndex + 2];
              marker1 = base64Data[dataIndex + 3];
  
              b1 = base64Alphabet[base64Data[dataIndex]];
              b2 = base64Alphabet[base64Data[dataIndex + 1]];
  
              if (marker0 != PAD && marker1 != PAD) {
                  //No PAD e.g 3cQl
                  b3 = base64Alphabet[marker0];
                  b4 = base64Alphabet[marker1];
  
                  decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
                  decodedData[encodedIndex + 1] =
                      (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
                  decodedData[encodedIndex + 2] = (byte) (b3 << 6 | b4);
              } else if (marker0 == PAD) {
                  //Two PAD e.g. 3c[Pad][Pad]
                  decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
              } else if (marker1 == PAD) {
                  //One PAD e.g. 3cQ[Pad]
                  b3 = base64Alphabet[marker0];
  
                  decodedData[encodedIndex] = (byte) (b1 << 2 | b2 >> 4);
                  decodedData[encodedIndex + 1] =
                      (byte) (((b2 & 0xf) << 4) | ((b3 >> 2) & 0xf));
              }
              encodedIndex += 3;
          }
          return decodedData;
      }
  
      /**
       * Check octect whether it is a base64 encoding.
       *
       * @param octect to be checked byte
       * @return ture if it is base64 encoding, false otherwise.
       */
      private static boolean isBase64(byte octect) {
          if (octect == PAD) {
              return true;
          } else if (base64Alphabet[octect] == -1) {
              return false;
          } else {
              return true;
          }
      }
  
      /**
       * Discards any characters outside of the base64 alphabet, per
       * the requirements on page 25 of RFC 2045 - "Any characters
       * outside of the base64 alphabet are to be ignored in base64
       * encoded data."
       *
       * @param data The base-64 encoded data to groom
       * @return The data, less non-base64 characters (see RFC 2045).
       */
      static byte[] discardNonBase64(byte[] data) {
          byte groomedData[] = new byte[data.length];
          int bytesCopied = 0;
  
          for (int i = 0; i < data.length; i++) {
              if (isBase64(data[i])) {
                  groomedData[bytesCopied++] = data[i];
              }
          }
  
          byte packedData[] = new byte[bytesCopied];
  
          System.arraycopy(groomedData, 0, packedData, 0, bytesCopied);
  
          return packedData;
      }
  }
  